Children could have been present inside the Manus Island detention centre during the two nights of rioting that saw one asylum seeker killed, another shot and dozens injured.

At least two asylum seekers held on Manus Island had declared themselves unaccompanied minors, according to two contractors who spoke to Guardian Australia independently. Both asylum seekers were present on Manus Island one day before the rioting occurred, but were being held among the adult population.

One of the asylum seekers was a Somalian who claimed to be 15 years old, the other was an Iraqi who is understood to have abandoned his claim after he was unable to source his birth certificate, and had planned to voluntarily return.

One contractor, who left Manus Island a day before the riot, said as many as five detainees who remained in the detention centre had claimed unaccompanied minor status.

Both the Somali and Iraqi asylum seekers were being held in Delta compound, a part of the centre understood not to be primarily affected by the rioting. It is understood that staff had been instructed to speak to the Somali boy every day to check his welfare.

The discovery of the two children on Manus Island in November led experts who constructed the age verification process of asylum seekers, which used psycho-social cognitive tests to determine contested ages, to deduce these tests had slipped.

A document seen by Guardian Australia from Manus Island highlights that any asylum seeker who claims they are an unaccompanied minor must produce documentary evidence of a birth certificate to prove their age, indicating that age verification tests are not conducted on Manus.

At a press conference on Friday Morrison said that, to his knowledge, there were no minors on Manus at the time of the riot.

“It is not the policy of the government for minors to be on Manus Island, where minors have been identified in the past, they’ve been promptly removed, and to my knowledge there are no minors on Manus island because that is not the policy of this government,” he said.